Process and apparatus for the development of latent electrostatic images



Oct. 4, 1966 VG. MARX ETAL 3,276,424

. PROCESS AND APPARATUS FOR THE DEVELOPMENT OF LATENT ELECTROSTATIC IMAGES Filed June 20, 1963 4 Sheets-Sheet 1 FIG. la

Fl-G.lb Fl6.ic

INVENTORS GERHARD MARX DETLEF WINKELMANN ATTO EY Oct. 4, 1966 MARX ETAL 3,276,424

PROCESS AND APPARATUS FOR THE DEVELOPMENT OF LATENT ELECTROSTATIC IMAGES 4 Sheets-Sheet 2 Filed June 20, 1963 FIG. 3

1N VEN TOR.S GERHARD MARX DETLEF WINKELMANN BY 6. if? 6 ATT NEY Oct. 4, 1966 G. MARX ETAL 3,275,424

. I PROCESS AND APPARATUS FOR THE DEVELOPMENT OF LATENT ELECTROSTATIC IMAGES Filed June 20, 1965 4 SheetsSheet 5 FIG. 4

IN V EN TOR.S

GERHARD MARX DETLEF WINKELMANN ATTO EY Oct. 4, 1966 MARX ETAL PROCESS AND APPARATUS FOR THE DEVELOPMENT OF LATENT ELECTROSTATIC IMAGES Filed June 20, 1965 4 Sheets-Sheet 4 FIG. 7

JNVENTORS GERHARD MARX DETLEF- WINKELMANN AT TOR United States Patent 3,276,424 PROCESS AND APPARATUS FOR THE DEVELOP- MENT OF LATENT ELECTROSTATIC IMAGES Gerhard Marx, Mainz-Kastel, and Detlef Winkelmann, Wiesbaden, Germany, assignors, by mesne assignments, to Azoplate Corporation, Murray Hill, NJ.

Filed June 20, 1963, Ser. No. 289,344 Claims priority, application Germany, June 22, 1962, K 47,053/62 9 Claims. (Cl. 118637) The invention relates to .a process and apparatus for the development of latent electrostatic images by wetting a supported image-bearing photoelectrically conductive insulator layer with a liquid developer, accompanied, if desired, by the application of an electric potential between the developer liquid and the uncoated side of the support.

In liquid development, use is made of variations, in the adhesive stress of the developer liquid on the surface to be developed, which result from the state of imagewise charging on the surface bearing a latent electrostatic image.

Liquid developers are in the form of a liquid having a composition such that it does not wet the uncharged areas of the material to be developed, but only those parts which are electrostatcally charged. Apart from the selection of the developer solutions, the intent in this process is to apply the developer liquid to the pho-toelectrically conductive insulator layer in such a way that rapid wetting and development of the image parts is effected without the application of too great an excess, which could adhere for purely mechanical reasons in a troublesome manner in the non-image parts.

Further, it should be possible for reversal images to be produced during the development process by additional application of fairly high potentials. For this reason, too, an excess of developer liquid should be avoided, so that there is no danger of liquid reaching the back of the material to cause short-circuiting and prevent the buildup of a potential of the magnitude necessary for the reversal development. Moreover, the back of the support must be electrically contacted approximately in the places where liquid is applied on the front. Usual processes, such as wiping over or passing through a container of liquid, do not produce uniform, entirely satisfactorily developed images with this development process. Nor, because of the different purpose for which they are intended, do processes and devices already known in coating practice or in the copying field give acceptable results, in particular because in the development of the areas carrying the latent image, no differences in the mechanical In the present process, the side of an electrophotographic material bearing a latent image is contacted with a liquid developer in a thin layer on the surface of a roll in a manner such that the electrophotographic material is advanced towards the surface of the roll, first in the direction of a chord, after which it is deflected by the surface of the roll to approximately the direction of a tangent. It is then further transported in the direction of this tangent, or further deflected in the direction of one or more tangents, by a device having at least two linear supports extending over the entire length of the roll and parallel to the axis thereof, a potential being optionally applied between the roll and at least one of the linear supports.

The invention also includes an apparatus for carrying out the process of the invention. The apparatus includes a liquid-supplying roll joined to a liquid-feeding system, one or more guide rails arranged at a slight distance from this roll, optionally in combination with at least one roll which determines the chord direction of approach of the electrophotographic material to the liquid-supplying roll, a first linear support arranged parallel to the roll axis and near the surface of the liquid-supplying roll in the direction of the chord, at least one further linear support arranged parallel to the roll axis and also arranged near the surface of the liquid-supplying roll in a manner such that it is in the direct-ion of advance of the material in the space between the surface of the liquid-supplying roll and the tangent made on the point of intersection of the roll surface and the chord or on this tangent and optionally an arrangement assisting discharge, e.g., discharge rolls or further guide rails and a voltage source the ends of which are connected with the liquid-supplying roll and with at least one of the linear supports.

The invention will be further illustrated by reference to the accompanying drawings in which:

FIGURE 1a is a schematic view in elevation of one embodiment of the apparatus of the invention,

FIGURE 11) is a fragmentary view in elevation of a modification of the apparatus of FIGURE 1a,

FIGURE 10 is a fragmentary view in elevation of a further modification of the apparatus of FIGURE 1a,

FIGURE 2 is a schematic view in elevation of a further embodiment of an apparatus of the invention,

FIGURE 3 is a schematic view in elevation of a further embodiment of an apparatus of the invention,

FIGURE 4 is a schematic view in elevation of a further embodiment of an apparatus of the invention,

FIGURE 5 is a schematic view in elevation of a further embodiment of an apparatus of the invention,

FIGURE 6 is a schematic view in elevation of a further embodiment of an apparatus of the invention, and

FIGURE 7 is a schematic view in elevation of a further embodiment of an apparatus of the invention.

Adjacent to the rotatable roll 1, two liquid-applying rolls 2, extending over the entire length of the roll 1, are mounted, with the aid of which a thin film of a developer liquid 4 from the trough 3 is applied to the surface of the roll 1. By means of a pair of feed rolls 5 an electrophotographic material is passed, in the direction of the arrow with the latent image side upward, to the surface of the roll 1. The leading edge of the electrophotographic material thus meets the surface of the roll.

The direction 16 is that of a chord of the roll 1 and this chord must be in the direction of running within the hatched semicircle of the roll 1 which is formed by a straight line passing through the meeting point of the electrophotographic material with the surface of the roll and the center of the roll. This direction is determined by the pair of feed rolls 5 and by the supporting surface 6 of the member described below which bears one or more linear boundary pieces, in combination with the surface 14 of the Wetting roll 13 mentioned below. A further guide member 7 can be mounted in front of the feed rolls as a further support.

The circumferential speed of the roll 1 is advantageously so selected that it is as fast as the feed speed of the sheet, as then neither the leading edge nor the trailing edge of the sheet becomes flooded with developer liquid.

At the surface of the roll, the electr-ophotographic material is defiected so that its direction is approximately that of a tangent 16a to the roll 1 and, in this way, it contacts a film of liquid on the roll 1.

The angle of deflection 5 between chord and tangent may vary within wide limits. Good results are obtained if this angle is between a fraction of a degree and about 45, preferably not more than 20. A certain pressure of the sheet against the roll results from the deflection, so that, even if the sheet has a tendency to curl, every element of the surface of the sheet comes into contact with film of liquid on the roll.

The further transport of the electrophotographic material in the direction of the previous tangent 16a is effected, as shown in FIGURE 1b, by the linear support b which lies on this tangent and extends over the entire length of the roll, being parallel to the axis of the roll and forming a component of member 8a. By this linear support, it is ensured that the electrophotographic material is not forced out of the direction of the tangent by the forces brought into play by the movement of the roll '1 or of the material itself. The guiding of the electrophotographic material being developed can also be effected by further linear supports, e.g., a member 811 with a third support 100 is shown in FIGURE 1c.

The electrophotographic material may, however, as shown in detail in FIGURE 1a and also in la, undergo a further deflection in the direction of one or more tangents, this deflection being introduced by means of at least one slope deflecting surface 10a. This ends in each case in a linear support 10 running over the entire length of the roll and parallel to the axis thereof. This support 10 projects into the space that is bounded by the surface of the roll and the tangent on the first contact point of the electrophotographic material with the roll 1, in the direction of travel of the material, i.e., during the development process the electrophotographic material contacts, in turn, the support 6 and the linear supports 6a and 10, after which the developed material, assisted, if desired, by a discharge slope can be removed from the apparatus.

In the apparatus just described, the sheet is not transported in the last portion of the process, after it has left the feed rolls. It is, therefore, advantageous for the member 8 and, where appropriate 8a and 8b also, to be set fairly high, so that the sheet may drop freely in the last part of the process down the discharge slope 15 or a conveyor belt, not shown, may be utilized which will discharge the sheet.

deflection produced by the surface of the roll and any further tangent or tangents should however, be kept small; it can vary from fractions of a degree to a few degrees. Advantageous development results can however be achieved if-with respect to the direction of the first deflection tangent-there is no further deflection.

The linear supports 6a and 10, or where appropriate 6b and 10b, or 6c, 6e and 100 may be formed as in FIG- ures la, 1b and 10, by members 8 and 8a or 8b with two or three sharp edges which form the linear supports. The notch between the edges. e.g., 11, as a result of which these project as ridges, is necessary for the described initiation of the further deflection as in FIGURE 1a and is also intended to prevent any small quantities of liquid brass is particularly suitable.

4i from accidentally coming between the roll and these parts. The liquid is then either removed by the rotating roll or flows away over parts 8 or 8a or 8b. In order that this process can be performed easily, it is advantageous for the latter parts not to be positioned directly under the roll.

The parts 8 to 8b, shown for example in FIGURES 1a, 1b and 10, may have any other form provided only that they meet the given requirements.

If a reversal development is to be performed with the process and apparatus of the invention, it must be ensured that, during wetting, a bias voltage can be applied between the developer liquid and the supporting material for the electrostatic image being developed and this should be effected as accurately as possible at the places where wetting occurs. This can be done very successfully with apparatus of the invention. As shown generally in FIG- URE 1a, the pair of feed rolls 5 and the member 8, when, for example, liquid reversal development of latent negatives on zinc oxide layers is desired, are connected with the positive pole of a current source of about 400 volts while the negative pole is connected to the roll and, hence, to the liquid. The voltage may however be raised to about 800 volts. Electrical contact between the two supporting lines 6a and 10 is normally adequate.

In the case of poorly conductive material, e.g. paper when atmospheric humidity is low, it is advantageous for contact to be improved by the application of a very thin film of conductive liquid, e.g. water, to the back of the support. For this purpose a damping device 12 with a damping roll 13 is provided on the surface 6 of the member 8. The damping roll may consist, for example, of sponge rubber or some other material that absorbs liquid. The supporting side of the electrophotographic material is drawn over the surface 14 before it comes into contact with the developer.

It is advantageous for the angle between the horizontal and the tangent or tangents, in the direction in which the paper contacts the roll, to be or more. The supporting points 10 or 10b or 100, which are on or within a tangent to the roll 1, are advantageously so arranged that in each case they are at the same distance, or, in the case of 10c double the distance from the contact point of the electrophotographic material with the roll 1.

The distance from one to the other of the supporting points may be between about 10 and 20 mm., when the diameter of the roll is about -80 mm. In general, distances of between 10 and 40 percent of the diameter of the roll 1 are preferable. Larger or smaller distances, however, still give successful results. The vertical gap between the roll and the linear support should be about l-2 mm. in the apparatus as described above. The upper supporting point should be set as near as possible to the point of intersection of the chord at which the sheet meets the roll and the tangent at which it passes the roll. The sheet then has a fairly small radius of curvature and lies better at the upper edge. This results in better contact, as described below.

A further factor of importance is the nature of the surface of the roll 1. Best results are obtained if superficial smoothness and resistance to corrosion are very high. Surfaces with high gloss polish, e.g., those made of metals or plastic, give the best results. However, a low-depth milling also gives serviceable results. High-gloss chromed The diameter of the roll, as shown in FIGURE 1, should advantageously be between 30 and mm., preferably between 40 and 60 mm.

Another embodiment of the apparatus is shown in FIG- URE 2. Here, member 8 of the apparatus of FIGURE 1 is replaced by a trough-type member 18 ending in a linear support and a supporting roll 17.

The electrophotographic material being developed is passed through the feed support int-o the apparatus where it is taken up by the feed roll 20, passed through the guide plate 19 and brought, in the direction of a chord to the roll 1, to the surface of the roll 1 and deflected. The latent image being developed now comes into contact with the film of liquid on the surface of the roll, while the back of the electrophotographic material runs over the two support lines 18a and 17a and is passed to the discharge chute 22.

If the electrophotographic material being developed is deflected in the direction of one tangent only, points 18a and 17a in FIGURE 2 correspond to points 6b and 10b in FIGURE lb. If the deflection in FIGURE 2 occurs in the direction of more than one tangent, the position of the points 18a and 17a in relation to the roll 1 corresponds to the position of the points 10 and 6a in FIG- URE 1, the deflecting surface 10a then being formed by the section 17b of the roll 17 in FIGURE 2.

Advantageously, the supporting roll 17 serves at the same time as a conveyor roll so that a very good feed of the electrophotographic material is ensured. The back of the material may be additionally moistened as the feed roll 20 dips into a trough of liquid 21.

Particularly advantageous results are obtained if the support roll 17 has a diameter such that the linear supports 18a and 17a have about the same distances from each other and from the roll surface as those described above in the case of the corresponding points 6a and 10 and 6b and 10b, respectively, in FIGURES 1a and 1b. Roll 17 as well as rolls 20 and 1, is motor driven.

FIGURE 3 shows a further form of the invention. Roll 1, the application rolls 2, as well as the ink trough 3, are generally the same as above. The electrophotographic material is introduced over the support 23, advanced by the motor-driven support roll 25 and carried under the guide plate 24 to the surface of the roll 1 where it is deflected and further transported over the two linear supports 25a and 26a, which are part of the supporting rolls 25 and 26. The latent electrostatic image is contacted with the liquid developer on the surface of the roll 1. The rolls 25 and 26 are preferably motor driven so that a trouble-free passage is ensured for the electrophotographic material. Here too, very good results are obtained if the linear supports 25a and 26a have a similar distance from each other, and from the surface of the liquid-bearing roll, as do the corresponding supports in FIGURE 1a or 1b. Member 27, with the wetting device 28-, here also improves the conductivity of the electrophotographic material by wetting the back of the sheet.

With the two last-described embodiments also, i.e. those of FIGURE 2 and FIGURE 3, a potential, e.g. up to about 800 volts, can be applied between the roll 1 and the members 18, 17, 2S and 26 in a manner analogous to that in the device of FIGURE 1. Neither short-circuiting nor breakdown by surface conductionoccurs before, during, or after the development process, so that reversal developments, in particular as described in US. Patent Number 2,956,487, can be very successfully performed. It is advantageous here that contact occurs in each case on the back of the sheet in those places where the developer has just wetted the surface of the electrophotographic material.

FIGURE 4 shows a further embodiment in which the side of the electrophotographic material which bears the .latent electrostatic image is passed over the support 30 between the feed rolls 29 and over the guide plate 31 in the direction of a chord to the surface of the roll 1 which carries the liquid developer film. The material is then deflected and strikes the deflecting surface 33. It is then advanced over point 32a to the discharge surface 32. The electrophotographic material may here too be tangentially deflected more than once. In this embodiment also, a voltage can be applied between the roll 1 and the parts 31 and 32.

FIGURE shows another embodiment which is preferable for many purposes, in particular for somewhat thicker electrophotographic papers. The electrophotographic material being developed, with the side bearing the latent image uppermost, is passed on a support 42 to the feed roll 39 which advances it over a wetting device 41, under a pressure spring 40, and over the linear support 43 to the surface of a roll 34 hearing the film of liquid developer. The electrophotographic material is deflected in the direction of a tangent, strikes the deflecting surface 44 and is then pushed over the point 45 on the support 42 to the exit. Here too the material rests against the roll 34 in the direction of one or more tangents. As a result of this slight pressure, the roll 34 is slightly lifted-a movement made possible by the sliding bearing 35.

The film of developer is applied in the embodiment of FIGURE 5, not by transfer rolls as in FIGURES 1-4, but by another system consisting of an applicator 38, in cluding a container 36 in which the liquid developer 37 is contained. When not in use, the roll closes the vessel 36 by its own weight and the roll is then, practically speaking, dry on the lower side thereof. When a sheet is passed under the roll, the latter is lifted a little, as already described. Developer can then run out at point 37b and is taken up by the rotating roll so that a film forms on the latter. Liquid that is not applied to the sheet is returned to the storage vessel as a result of the rotation of the roll.

A further embodiment which permits of particularly simple handling is show in FIGURE 6 in which the roll 1 of FIGURE 1 is replaced by the roll 55 having a much smaller diameter. The liquid applicator system includes the container 57 for the liquid developer, an intermediate container 56 connected thereto which also connects to a cylindrical recess in which the easily rotatable roll 55 is fitted. Parts 55-57 are enclosed in a housing 58 of solid construction.

When the apparatus is not in operation, the roll rests by its own weight on the lower edges of points that project somewhat below the recess and prevents the developer from running out.

During the development process, the electrophotographic material, which is pushed through under the roll, raises the roll slightly. As a result, the developer liquid covers the surface of the entire roll, which is rotating, with a thin film of liquid and thereby brings the liquid developer into contact with the latent electrostatic image.

Similarly to the operation of the preceding embodiments, the electrophotographic material is fed from a supporting surface 46 by one or two feed rolls 47 and passed, in the direction of a chord, to the roll 55 over a wetting system 48, under a pressure spring 49 and over the linear support 50. On the surface of the roll, the electrophotoraphic material, similarly to the preceding embodiments, is deflected and pushed over the surface 52 and the edge 53 to the discharge 54. At the conclusion of the development process, i.e., when the trailing edge of the electrophotographic material has passed the edge 53, the roll 55, as described above, closes the outlet for the liquid developer. Should traces of liquid continue to drip, the trough 51 catches the liquid without the back of the succeeding electrophotographic material being affected in an undesirable manner.

In FIG. 7, a further modification of the apparatus according to the present invention is shown which is particularly suitable for higher rates of travel and which also produces excellent copies. With this apparatus, sheets of side DIN A 2 and larger may be easily developed. In this case, the electrophotographic material to be developed is passed, with the side carrying the latent image facing downwardly, over a feed table 59 to the rolls 60 and 62. The roll 62 is preferably motor driven, while the metal roll 60 is loosely pressed against the roll 62 by its own weight and, because of a movable axis 61, ensures a good pick-up and transport of the material to be developed. In a preferred embodiment of the invention,

the surface of the roll 62 may be covered with soft rubber.

By means of the deflection abutment 64, the electrophotographic material is passed between the rolls 62 and 65. The end of the deflection abutment and the passage between the rolls are so arranged with reference to each other, that the material is .guided in the direction of a chord to the roll 63 carrying the liquid developer.

The aforementioned roll 65 is a damping roll which carries on its surface a thin film of a liquid, preferably water. It is of advantage if this roll is covered with a foam-like plastic which absorbs the liquid to be applied. By means of the damping roll 65, the material to be developed is evenly moistened on the surface away from the image side. The roll 65 is, in turn, moistened by a roll 66 which dips into a bath 69, preferably water. The degree of moistening of the roll 65, i.e. the thickness of the film of liquid, may be adjusted by regulating the distance between the axes of the rolls 65 and 66.

The damping liquid 69 is taken from a container 68,

which may be connected by means of a pipe 70 with a source of supply and, if desired, ing the level of the bath 69.

The travel of the material to be developed in the direction of a chord 75 to the applicator roll 63 may be assisted by means of a guide 72. The material is also guided by the upper supporting surface of the member 71 which is provided with two linear supports 71a and 71b. Deflection in the direction of a tangent 74 is effected by this member, in the manner described above. Thus the image side of the electrophotographic material is contacted with the liquid developer film covering the surface of the roll 63, so that development is effected.

The liquid developer is applied to the surface of the roll 63 by the rolls 76 and 77. Rolls 63 ad 77 preferably consist of smooth, highly alloyed steel and are fixedly mounted while roll 76 is adjustably mounted in movable bearings. In this manner, the thickness of the liquid film on the applicator roll may be varied. The surface of the steel roll 76 is preferably provided with a plastic cover, e.g. of polyvinyl chloride. It has been found that an optimum thickness of the liquid developer film on the roll 63 is obtained when the distance between the rolls 76 and 77 is from about to 70p and that between rolls 76 and 62 is in the range of about 200 to 300p..

The lower part of the roll 77 is immersed in a supply of liquid developer 80 contained in a vessel '79. Here, too, a connection 78 may be provided to a source of supply and to the vessel. In order to remove or reduce any residues of unused liquid developer (not shown) when the apparatus is not in operation, doctor and spraying devices may be attached in known manner to the rolls 76, 77 and 63.

After the electrophotographic material has contacted the developer liquid, it is conveyed in the direction of the surface of the guide roll 67. The surface of this roll may be in a tangent to or may from a small angle away from the roll 63. By this arrangement, a good development of the trailing edge of the sheet is also ensured, since, due to the weight of the electrophotographic material to be developed, it presses against the film of liquid developer on the roll 63 even after leaving the passage between the rolls 62 and 65. The roll 6"] is preferably driven. Also, in the interest of a complete development, the discharge table is arranged at a small angle to the tangent. The discharge table may consist of contiuous plastic material or of metal guide pins. This also considerably reduces the curling tendency of the developed copies. The electrical devices and connections are not shown in the drawings in the interest of clarity.

The rolls mentioned above may be driven in known manner by chains and sprockets. The rolls and the nonremovable parts are preferably mounted in plastic side plates in which ball bearings in races are secured.

As described above, the apparatus may be used with with a device for adjustthe application of a bias voltage of 50 to 800 volts, in which case the poles are advantageously connected to the roll 63 and the member 71.

The process and apparatus of the invention enable electrophotographic material to be very rapidly developed. Development speeds of about 20 cm. per second give excellent results. It is also possible, however, to exceed these speeds or to operate below them and still obtain very good image quality.

Both cut sheets, e.g., sizes DIN A 5 to DIN A 1, and endless electrophotographic material wound on a roll can be processed with equal facility. In the latter case feed rolls and other devices to transport the developed material after it leaves the development zone can be dispensed with if the Winding and unwinding devices are controlled.

No current break-through occurs during the development process. The elements of the device are so arranged that, both before and after development, switching off of the current is unnecessary. Because of the gaps between the roll carrying the development fluid and the linear constructions or drain devices, there is always adequate space when electrophotographic material is not present, to prevent break-through of current.

By the use of the invention, images of, great marginal sharpness, high contrast and virtual freedom from background are obtained. Development results can be reproduced with any number of images in an always uniform manner.

It will be obvious to those skilled in the art that many modifications may be made within the scope of the present invention without departing from the spirit there of, and the invention includes all such modifications.

What is claimed is:

1. An apparatus for developing a latent electrostatic image which comprises a rotatable roll for applying developer to the image, means for applying developer to the roll, means for introducing an edge of an electrophotographic material bearing an electrostatic image against the roll in the direction of a chord of the latter, a first stationary linear support mounted parallel to the roll axis adjacent the surface of the roll in the direction of the chord whereby the electrophotographic material is bent and forced against the developer on the surface of the roll, and at least one additional stationary linear support mounted parallel to the roll axis between the roll surface and a line tangent to the roll surface at the point of intersection of the latter with the chord whereby the electrophotographic material is further guided after initial contact with the roll.

2. An apparatus according to claim 1 in which the additional linear support is positioned on a line tangent to the roll surface at the point of intersection of the latter with the chord.

3. An apparatus according to claim 1 in which there are three linear supports.

4. An apparatus according to claim 1 in which means are included for applying a potential between the roll and at least one of the linear supports.

5. An apparatus according to claim 4 in which means are included for wetting the image-free side of the electrophotographic material.

6. An apparatus according to claim 1 in which the distance between the linear supports is between about 10 and 40 percent of the diameter of the roll.

7. An apparatus according to claim 1 in which the distance between the linear supports and the surface of the roll is about 1 to 2 mm.

8. An apparatus according to claim 1 in which the roll is fabricated of metal having a smooth surface.

9. An apparatus according to claim 1 in which the means for applying developer to the roll includes a channel capable of being closed by the weight of the roll.

(References on following page) 9 10 References Cited by the Examiner 3,084,043 4/ 1963 Gundlach 117-37 X I D P 3,096,198 7/1963 Schaifert 117-37 X UN TE STATES ATENTS 3,124,484 3/ 1964 Magnusson 118637 2/1891 Knowlton et a1. 118236 X 6/1933 Steffen 118-251 5 OTHER REFERENCES 9/1937 Carlson. Day, 1.: Mensuration, p. 14, Durride and Peck, New 9/1944 Carlson 117-175 X Haven, 1839- E 117111 X WILLIAM D. MARTIN, Primary Examiner.

o nson 1 4/1963 Carlson 118256 0 G. L. HUBBARD, Asszstant Exammer. 

1. AN APPARATUS FOR DEVELOPING A LATENT ELECTROSTATIC IMAGE WHICH COMPRISES A ROTATABLE ROLL FOR APPLYING DEVELOPER TO THE IMAGE, MEANS FOR APPLYING DEVELOPER TO THE ROLL, MEANS FOR INTRODUCING AN EDGE OF AN ELECTROPHOTOGRAHPIC MATERIAL BEARING AN ELECTROSTATIC IMAGE AGAINST THE ROLL IN THE DIRECTION OF A CHORD OF THE LATTER, A FIRST STATIONARY LINEAR SUPPORT MOUNTED PARALLEL TO THE ROLL AXIS ADJACENT THE SURFACE OF THE ROLL IN THE DIRECTION OF THE CHORD WHEREBY THE ELECTROPHOTOGRAPHIC MATERIAL IS BENT AND FORCED AGAINST THE DEVELOPER ON THE SURFACE OF THE ROLL, AND AT LEAST ONE ADDITIONAL STATIONARY LINEAR SUPPORT MOUNTED PARALLEL TO THE ROLL SURFACE AT THE ROLL SURFACE AND A LINE TANGENT TO ROLL SURFACE AT THE POINT OF INTERSECTION OF THE LATTER WITH THE CHORD WHEREBY THE ELECTROPHOTOGRAPHIC MATERIAL IS FURTHER GUIDED AFTER INITIAL CONTACT WITH THE ROLL. 